# Matrix problem

Given the matrix
A= [a 1 9]
[a -6 3]
[5 -8 a]

find all values of a that makes

a can be _ & _

NEED HELP! IM BEYOND STUCK! I have no idea to even approach this problem! Thanks!

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$$$\left| {\left. {\bf{A}} \right|} \right. = 285 - 48a - 7a^2 = 0$$$